Electrical contact with various portions of the body through a transvenous approach has found increasing interest in recent years. Of particular interest is a reliable endocardial electrical contact with the atrium. Such a contact allows atrial pacing or atrial synchronized pacing without a thoracotomy thereby preserving the contribution of atrial contraction in the overall cardiac output while significantly lowering patient risk and morbidity. Additionally, an atrial contact would be advantageously employed for arrhythmia management and other purposes which may not be accomplished through ventricular electrical stimulation. For reasons well known to those skilled in the art, the greatest advantages from an electrical contact with the heart can be obtained by contacting the right atrium, the right atrial appendage providing a suitable site.
In the U.S. Pat. application Ser. No. 372,269, of Paul Citron and Eugene A. Dickhudt, filed June 21, 1973, now U.S. Pat. No. 3,902,501 and commonly owned with the present application and incorporated herein by reference, there are discussed several prior attempts to accomplish an endocardial electrical contact with the atrium. Part of that discussion centers upon a paper co-authored by me which described a J-shaped catheter with a flange near the tip. The catheter was inserted into the right atrium through a transvenous approach after being straightened by the insertion of a stylet. The catheter assumed its preformed J-shape within the atrium to facilitate placement of the electrode tip in the artrial appendage when the stylet was withdrawn. The atrial trabeculae and shape of the catheter were relied upon to maintain the lead in location until the heart tissue itself enveloped and fixed the tip.
A sensing atrial endocardial electrode is also described in the referenced patent application. This prior art electrode employed a J-shaped applicator catheter which was used to direct the electrode tip into the right atrial appendage. The lead was provided with two fine wire hooks positioned at its tip each ending in a relieving loop. The hooks were held back by the applicator catheter to spring out and anchor the electrode in the trabeculae of the right atrial appendage when the electrode tip left the end of the applicator catheter.
The deficiencies in the prior art techniques described above are detailed in the referenced patent application which provides a novel electrode uniquely adapted for use as an atrial endocardial electrode. In essential part, the lead of the referenced patent application, as shown in FIG. 1 thereof, is comprised of a body member terminating at an exposed electrically conductive tip having a plurality of tines extending at an acute angle from the body member from a position adjacent the tip. As so constituted, the tines will become involved with the cooperating trabeculae of the right atrial appendage to push against them and maintain the tip in electrical contact with the inner wall of the right atrial appendage. For this purpose, it is contemplated that the tines extend generally around the circumference of the body member with the number of tines not being critical to the operativeness of the invention. The tines of the referenced patent application are intended to push against the coperating trabeculae to urge the lead in a direction defined generally by its longitudinal axis. This, the tines of the referenced patent application are effective to urge only the terminus or tip of its lead into electrical contact with the inner wall of the atrial appendage, or similar organs or chambers.